Cutaneous basophil hypersensitivity (CBH) is the name that has been given to delayed-in-time reactions which have been found to contain basophils. This newly described recruitment of basophils into delayed reactions has opened a vitally important area of research into basophil function. Regulation of these cells in delayed reactions has been linked to immune lymphocytes and immune serum through mechanisms that are not totally understood. This research proposal presents plans for a more in-depth investigation of the immune mechanisms controlling basophil recruitment into delayed hypersensitivity. CBH has been best studied in the guinea pig and in this species an antigen specific 7SIgG1 antibody fraction of serum has been shown to mediate cutaneous basophil hypersensitivity. In this study experiments are planned to evaluate in detail the hypothesis that the Fc portion of the 7SIgG1 molecule is important in the mediation of CBH. Cutaneous basophil hypersensitivity reactions resemble the newly recognized IgE mediated late component of immediate anaphylactic hypersensitivity reactions. With this in mind, studies have been designed to investigate the possibility that guinea pig IgE can mediate CBH as a model for the human late reactions. Experiments have also been outlined to examine the question of an interrelationship between T cells and B cells in the regulation of CBH. The possibility that T cell transfers of basophil responses are dependent on contaminating donor B cells or B cells in the recipients will be investigated.